What is a thyroid gland ?The thyroid gland is a small organ in the midline of the neck, just below the Adam's apple (larynx).It is easy to recognize a thyroid swelling- it moves up on swallowing !The function of the thyroid gland is to make a hormone called 'thyroxine'. A normal amount of thyroxine is required for normal physical and mental development. In adults, thyroxine keeps cells and tissues working at just the right metabolic rate.What can go wrong with it ?However, lumps or masses can arise in the thyroid causing different thyroid diseases. A visible enlargement of the thyroid gland is called Goitre. The entire gland may be involved or there may be single or multiple nodules or lumps. Thyroid masses can also be associated with hormonal imbalance. Patients with overactive or under-active thyroid glands can have goitre but most goitres produce a normal amount of thyroxine.An overactive thyroid gland would produce too much thyroxine causing hyperthyroidism The symptoms of this condition include tremor, heat intolerance, irritability, increased energy, poor sleep, weight loss and frequently, bulging eyes. Patients generally have a high metabolic rate.Too little thyroxine from an under-active gland causes an illness with a low metabolic rate called hypothyroidism. This condition causes tiredness, weight gain, swelling and slowness of speech and thinking.Single NoduleA single swelling or lump (nodule) in the thyroid gland is a special form of goitre. The majority (90%) of the nodules are not cancerous but either simple swellings of fluid (cysts) or benign growths of thyroid tissue with no tendency to spread or invade structures.The remaining 10% are usually a very low-grade form of cancer, which is almost always completely curable. There are a very small number of nodules that turn out to be a more aggressive form of thyroid cancer, these occur in special situations and are very rare.Multinodular Goitre (MNG)Frequently the lumps are not single but multiple and part of an innocent, non-cancerous condition called MNG, which just means that several swellings are present. Occasionally they can be later found to harbour cancer cells !CystCysts (fluid collections) in the thyroid are common. Frequently they are present without the patient noticing but sometimes they can enlarge so that they can be felt. Colloid NodulesThese are benign nodules made up of thyroid tissue that have become enlarged. They can be single or multiple and can sometimes become very large. Surgery becomes necessary if the nodule becomes large and causes compressive symptoms or if they cause cosmetic deformity.Non-Cancerous TumoursThese tumours (generally 'adenoma') are caused by an abnormal growth of thyroid follicle cells. They have no capacity to spread or cause destruction of tissue but they cannot be differentiated from one of the types of thyroid cancer on FNAC (please see next column). Surgery is usually recommended for diagnosis. Thyroid CancersThe most common thyroid cancers are differentiated thyroid cancers named either papillary or follicular cancer. T h e s e make up more than 90% of thyroid cancer and they very rarely cause death. They do have the potential to spread to lymph nodes in the neck and to other parts of the body such as the lungs but even if they do, these tumours are still treatable. Surgery is necessary in most cases.So what are the complications?Goitres, especially MNG, can become very large and cause pressure on the windpipe (trachea) and swallowing tube (oesophagus). This can result in shortness of breath, voice change, cough, increased pressure sensation in the neck and sometimes difficulty swallowing.Surgery to remove the thyroid gland is usually necessary to treat large goitres that are causing symptoms. Surgery is also necessary where there is a suspicion of thyroid cancer in an enlarged thyroid gland and where the swelling is causing cosmetic deformity.So, how is a thyroid problem diagnosed?1. An ultrasound scan may be requested to measure the shape of the thyroid and to look for nodules or cysts within the gland. 2. Fine needle aspiration cytology (FNAC). This is an extremely valuable test for diagnosing thyroid lumps. A small sample of cells or fluid is removed from the thyroid gland by passing a needle through the nodule or cyst in the gland. The aspirate is then examined under the microscope and the type of cells making up the swelling can be seen. The test is usually 80-90 percent accurate. Histology (Study of the cells making up the sweling) of the mass in question is important to differentiate a cancerous and non-cancerous type, and further to that, which particular subtype of cells. This in turns makes a big difference in the subsequent treatment of the mass.
This patient education is provided in good faith to help patients and their families learn more about their medical conditions, the options available to them and the possible consequences of their decisions. This information is not intended to be used for diagnosis, or treatment of any specific individual. Please consult with your ENT doctor regarding your particular circumstances.
Alternatively, FNAC can be more accurately performed under ultrasound guidance, called ultrasound-guided FNAC. It is more superior for deep-seated masses as the ultrasound allow a real-time precise targeting of the needle into the lesion in question (analogy is a soldier wearing a night-vision infra-red goggle in pitch-black darkness shooting at a target !) Other than thyroids, this technique can also be applied to other head and neck masses, as in here.The advantages of ultrasonography is that it is rapid, inexpensive, versatile, no ionizing radiation (eg. CT scan, X ray) is applied, does not require injection of contrast medium and can be easily repeated when necessaryUltrasound guided fine needle aspiration cytology (FNAC) is a safe diagnostic procedure in which any structure visualized can be reached quickly and precisely by a fine needle in any desired plane with constant visualization of the needle tip during insertion.3. Endoscopic examination of the vocal cordsto exclude potential involvement of the nerve (recurrent laryngeal nerve RLN) supplying the vocal cords pre- and post-surgery. This can be done in the outpatient clinic after applying some local anaesthetic nasal spray.As a thyroid cancer may infiltrate into the nerve supplying the vocal cord muscles, similarly the thyroid surgery itself may potentially affect the function of the nerve, it is vital to know the status of the voice box (vocal cords) before and after the surgery. Any vocal cord weakness can affect the voice and swallowing function..
4. CT scanmay be necessary if there is recurrent goitre, thyroid cancer with involved lymph nodes or a large retrosternal (a thyroid gland that grows into the chest cavity) thyroid causing compression. CT is not usually indicated for smaller palpable thyroid lumps.5. Blood tests looking for the function of the gland (free T4, TSH), thyroid antibody levels, thyroglobulin levels may be needed.The final management of the patient, surgical or non-surgical, would very much depend on the symptoms and the results of the investigations. Surgery may be needed in symptomatic or large thyroid swellings and if cancer is suspected.
An ultrasound of the neck in progress, with the red arrow showing the probe
An ultrasound image of a thyroid mass (the blue line showing the approximate size)
DR. VINCENT TANConsultant Ear, Nose and Throat, Head and Neck Surgeon,MD (UKM), MS ORL-HNS (UKM), DOHNS RCS Edinburgh (UK), MRCS Edinburgh (UK), Postgrad. Cert.in Allergy (UK), A.M. (Mal), Fellowship in Rhinology (Singapore)Fellowship in Head and Neck Oncology & Surgery (Amsterdam)